Propagate **kw in postgresql distinct on compilation

Fixed bug in PostgreSQL dialect where compiler keyword arguments such as
``literal_binds=True`` were not being propagated to a DISTINCT ON
expression.

Fixes: #4325
Change-Id: I9949387dceb7fabe889799f42e92423572368b29

1 files changed, 7 insertions, 0 deletions

diff --git a/test/dialect/postgresql/test_compiler.py b/test/dialect/postgresql/test_compiler.py
index 5c4d72c67..6133ab482 100644
--- a/test/dialect/postgresql/test_compiler.py
+++ b/test/dialect/postgresql/test_compiler.py
@@ -1571,6 +1571,13 @@ class DistinctOnTest(fixtures.TestBase, AssertsCompiledSQL):
             "SELECT DISTINCT ON (t.a) t.id, t.a, t.b FROM t"
         )
 
+    def test_literal_binds(self):
+        self.assert_compile(
+            select([self.table]).distinct(self.table.c.a == 10),
+            "SELECT DISTINCT ON (t.a = 10) t.id, t.a, t.b FROM t",
+            literal_binds=True
+        )
+
     def test_query_plain(self):
         sess = Session()
         self.assert_compile(